This invention relates to the manufacture of semiconductor devices and more particularly to a semiconductor device geometry primarily useful for power semiconductor devices and to a method of manufacturing devices of that geometry, the method incorporating temperature gradient zone melting techniques.
All but the largest semiconductor devices are normally manufactured from wafers of semiconductor material of sufficient size to form several devices. Thus, a plurality of devices is processed simultaneously in wafer form. Following the formation of the devices in wafer form, the wafer is subdivided to form individual device pellets which are then packaged as desired. All of the above is well known in the prior art.
Many power semiconductors are now passivated, usually with glass. When a plurality of semiconductor devices is made in wafer form, glassivation is usually begun by grooving each face of the wafer to expose the voltage blocking junctions. The grooves on each side of the wafer are generally in registration. (See, for example, U.S. Pat. No. 3,644,801 issued to Gary S. Sheldon on February 22, 1972, and assigned to the assignee of the present invention.) Glass is deposited in the grooves and then the wafer is subdivided and packaged by conventional techniques.
A problem that occurs when manufacturing glass passivated devices in the aforementioned manner is that the registered grooves sometimes weaken the semiconductor wafer to the point that wafer breakage during subsequent processing steps reaches an unacceptably high level. This problem can, of course, be alleviated by foregoing glass passivation. However, for many demanding applications, the superior electrical properties and reliability of glass or high quality passivation are extremely important.
It is, therefore, an object of this invention to provide a semiconductor device with superior properties, and, to provide a method for manufacturing the device which alleviates the problem of wafer breakage.